The invention relates to the field of chemical analysis, particularly identification of analyte substances within samples such as liquid samples.
Techniques have been developed for the analysis, or detection of the presence, of substances, such as organic compounds, within samples such as samples of biological fluids. For instance, samples of human blood, saliva, urine, etc., can be tested for the presence of drugs of abuse. In many cases, the substances to be detected may be present in small quantities, or at low concentrations, within the sample.
Although analytical instrumentation is becoming increasingly sensitive, and analyte detection continues to improve, chemical analytes in solution sometimes must be concentrated, prior to chemical analysis. Typically, such concentration is done using bench-top chemical processes specifically developed or tailored to the analytical problem at hand. Such processes include, for instance, solvent condensation or evaporation techniques that eliminate the solvent while retaining the analyte, by exploiting differences in physical properties such as volatility.
In gas chromatography (GC), large volume injection techniques have been developed with special hardware, such as pre-column inlets, to allow more sensitive detection by evaporation of solvent, while attempting to retain analyte inside the pre-column inlets prior to the analyte being delivered to the analytical column for chromatographic separation and analysis/detection.
For the testing process, the samples are handled in vials, test tubes, etc. Loss or contamination of the sample should be eliminated or kept to a minimum, and the equipment for handling the samples is designed with that in mind.
In one example of a testing scenario, a relatively large (for instance, greater than 2 ml) sample volume is to be processed by condensation to a smaller volume (for instance, less than 1 ml) prior to injection into instrumentation such as gas chromatography or liquid chromatography equipment. Condensation may be done by heating the sample, exposing the sample to a stream of gas to facilitate evaporation of volatile solvent, or some combination of these or other techniques.
Such condensation improves detection limits, by enabling a larger fraction of the total sample to be analyzed. However, the condensation requires the sample, which initially is in a larger volume container, to be transferred to a smaller volume container, such as a standard chromatography vial, or a vial with an integrated insert. These vials typically have volumes less than 2 ml, and fit inside standard automated liquid sampler systems.
In co-pending U.S. patent application Ser. No. 10/947844, Prest, “Method and Article for Analyte Concentration Free of Immediate Transfer,” there is described a method and apparatus for concentrating an analyte directly into a test receptacle. A liquid containing an analyte is placed into a first receptacle, which is in direct fluid communication with a second receptacle. The analyte is concentrated, into the second receptacle, by known processes. The second receptacle is then used, to provide the concentrated analyte to an instrument for analysis, without liquid transfer and without loss of analyte.
However, the volume of analyte injected is usually small. As a consequence, repetitive (manual or automated) transfers and condensation steps are required to complete the transfer of the larger volume. Each of these transfer steps is subject to possible loss, and the total transfer process therefore is labor intensive. Also, rinses of the original sample container are required to minimize losses on the surfaces. This process is itself frequently subject to losses, and so is seldom fully quantitative.
There is provided an apparatus for concentrating an analyte, comprising a first receptacle having a first aperture, the first aperture having a first configuration; and a second receptacle having a second aperture, the second aperture having a second configuration. The first configuration and the second configuration are complementary, such that the first and second apertures engage each other at a sealing surface. Analyte solution within the first receptacle passes into the second receptacle substantially without leaking at the engaged first and second apertures.
Further features and advantages of the present invention, as well as the structure and operation of preferred embodiments of the present invention, are described in detail below with reference to the accompanying exemplary drawings.